Protective effects of α-1 antitrypsin on human islets injury after transplantation by pancreas exocrine cells

Abstract

Objective To investigate the protective effects of α-1 antitrypsin on human islets injured by protease released from pancreas exocrine cells. Methods ( 1 ) in vivo experiment. Parts of the cadaveric pancreas was digested with collagenase, islets were selected artificially, and pancreatic exocrine cells were collected. 8-9 weeks olds male BALB/c-Nu nude mice were induced into diabetic mice with STZ (240 mg/kg body weight, i. p) and randomly divided into two groups: the control group (n = 6), 250 islets were transplanted into left kidney subcapsule of diabetic nude mice; cotransplant group (n = 7), 250 islets and the equal volume of pancreatic exocrine cells were transplanted into different regions of left kidney subcapsule. Blood glucose level was monitored. Nephrectomies were performed after 28 days. The expression of anti-amylase antibodies in subcapsule was detected by using immunohistochemical staining. (2) Islets culture: Three groups were randomly set up. Group 1: purified islet group, 250 islets were incubated into a 6-well culture plate; Group 2: non-purified islet group, 250 purified islets and equal volume of exocrine cells were incubated; Group 3: nonpurified islet + Al AT group, 250 purified islets and equal volume of exocrine cells were incubated with α-1 antitrypsin added (0. 5 mg/ml). After 48 h, insulin content of islets in each well and trypsin concentration in the supernatant of each well were measured. Results 10000 islets were collected.After islets transplantation, the blood glucose levels in control and co-transplant groups were normal,but a delayed islet function in reversing diabetes was in the co-transplant group, and ehe mice in both groups became hyperglycemic after nephrectomy. A large number of anti-amylase antibody-positive cells were found in renal subcapsule in the co-transplant group while little seen in the control group.Insulin levels in the non-purified islet group were decreased as compared with purified islet group,those in the non-purified islet group + A1AT group were higher than in the non-purified islet group,but lower than in the purified islet groups. Trypsin concentration in the non-purified islet group was increased as compared with purified group, that in the non-purified islet group + A1AT group was lower than the non-purified islet group, but higher than in the purified islets group (all P＜0. 01).Conclusion Protease released from acinar cells during pancreatic digestion has detrimental effect on islet function after transplantation. Co-cultivation of islets and pancreatic exocrine cells with A1AT added can prevent islet cell damage caused by trypsin. Key words: Islet transplantation; exocrine cells; amylase; α-1 antitrypsin